Semiconductor device having concentration difference of impurity element in semiconductor films

ABSTRACT

To provide a semiconductor device having a memory element, and which is manufactured by a simplified manufacturing process. A method of manufacturing a semiconductor device includes, forming a first insulating film to cover a first semiconductor film and a second semiconductor film; forming a first conductive film and a second conductive film over the first semiconductor film and the second semiconductor film, respectively, with the first insulating film interposed therebetween; forming a second insulating film to cover the first conductive film; forming a third conductive film selectively over the first conductive film which is formed over the first semiconductor film, with the second insulating film interposed therebetween, and doping the first semiconductor film with an impurity element with the third conductive film serving as a mask and doping the second semiconductor film with the impurity element through the second conductive film.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to semiconductor devices and methods ofmanufacturing the semiconductor devices. In particular, the presentinvention relates to semiconductor devices including memory elements andmethods of manufacturing the semiconductor devices including memoryelements.

2. Description of the Related Art

In recent years, semiconductor devices have been improved significantly.As integration and density of semiconductor devices become higher,miniaturization of various element patterns therein such as transistorsor capacitors has been rapidly progressed. There are strong demands forsemiconductor devices which are small in size and large in capacity andcan be manufactured at low cost. To fulfill such demands, it isessential to further miniaturize various element patterns. As well asreduction in size of transistors, memory elements, capacitors, and thelike for reducing an area occupied by such elements, manufacture of suchelements at low cost are necessary. Development of structures of suchelements has been actively conducted to meet the need.

For example, in Patent Document 1 (Japanese Published Patent ApplicationNo. 2000-269512), in a pixel matrix circuit including thin filmtransistors, a capacitor (a transistor-type capacitor) has one electrodeof a semiconductor film which is doped with an impurity element, theother electrode of a conductive film which corresponds to a gateelectrode of a transistor, and an insulating film between the twoelectrodes which corresponds to a gate insulating film of thetransistor, so that capacitance per unit area is increased. Therefore,an area occupied by elements is reduced in the device of Patent Document1.

SUMMARY OF THE INVENTION

In a case where a capacitor has one electrode of a semiconductor filmwhich is doped with an impurity element and the other electrode of aconductive film corresponding to a gate electrode of a transistor, thefollowing steps are required: forming a semiconductor film over asubstrate, doping a part of the semiconductor film which is included inthe capacitor with an impurity element at high concentration; and then,forming a gate electrode. This is because a part of the semiconductorfilm which is included in the transistor is to be doped with an impurityelement at high concentration in a self-alignment manner with the gateelectrode serving as a mask. Therefore, there arise problems of increasein cost due to increase in the number of manufacturing steps andcontamination to the part of the semiconductor film which is notsubjected to the doping with the impurity element at high concentrationbefore the formation of the gate electrode.

To avoid such problems, a semiconductor film which is not doped with animpurity element may be used as one electrode of a transistor-typecapacitor; however, if voltage applied to the other electrode of thetransistor-type capacitor is lower than a threshold voltage of thetransistor-type capacitor, the transistor-type capacitor may fail tofunction as a capacitor.

With view of the foregoing problems, it is an object of the presentinvention to provide a method with a simplified manufacturing processfor a semiconductor device. In addition, it is an object of the presentinvention to provide a semiconductor device including a memory element,in which an area of a capacitor is reduced.

The present invention relates to a method of manufacturing asemiconductor device including a capacitor in which an insulating filmis interposed between two electrodes. In the capacitor, a semiconductorfilm serving as one of the electrodes is doped with an impurity elementthrough the insulating film and a conductive film serving as the otherelectrode. In addition, the semiconductor film serving as the one of theelectrodes is formed at the same time as a semiconductor film which isincluded in a memory element formed over the same substrate as thecapacitor, and the conductive film serving as the other electrode of thecapacitor is formed at the same time as a conductive film (also referredto as a charge storage layer or a floating gate) which is included inthe memory element. Hereinafter, a semiconductor device of the presentinvention and a method of manufacturing the semiconductor device aredescribed in detail.

A method of manufacturing a semiconductor device, according to oneaspect of the present invention, includes forming a first semiconductorfilm and a second semiconductor film over a substrate; forming a firstinsulating film to cover the first semiconductor film and the secondsemiconductor film; forming a first conductive film and a secondconductive film over the first semiconductor film and the secondsemiconductor film, respectively, with the first insulating filminterposed therebetween; forming a second insulating film to cover thefirst conductive film; forming a third conductive film selectively overthe first conductive film which is formed over the first semiconductorfilm, with the second insulating film interposed between the firstconductive film and the third conductive film; and doping the firstsemiconductor film with an impurity element with the third conductivefilm serving as a mask and doping the second semiconductor film with theimpurity element through the second conductive film.

A method of manufacturing a semiconductor device, according to anotheraspect of the present invention, includes forming a first semiconductorfilm, a second semiconductor film, and a third semiconductor film over asubstrate; forming a first insulating film to cover the firstsemiconductor film, the second semiconductor film, and the thirdsemiconductor film; forming a first conductive film and a secondconductive film selectively over the first semiconductor film and thesecond semiconductor film, respectively, with the first insulating filminterposed therebetween; removing the first insulating film which isformed over the third semiconductor film; forming a second insulatingfilm to cover the first conductive film, the second conductive film, andthe third semiconductor film; forming a third conductive filmselectively over the first conductive film which is formed over thefirst semiconductor film, with the second insulating film interposedbetween the first conductive film and the third conductive film; forminga fourth conductive film selectively over the third semiconductor filmwith the second insulating film interposed therebetween; and doping thefirst semiconductor film with an impurity element with the thirdconductive film serving as a mask, doping the third semiconductor filmwith the impurity element with the fourth conductive film serving as amask, and doping the second semiconductor film with the impurity elementthrough the second conductive film.

A method of manufacturing a semiconductor device, according to anotheraspect of the present invention, includes forming a first semiconductorfilm, a second semiconductor film, and a third semiconductor film over asubstrate; forming a first insulating film to cover the firstsemiconductor film, the second semiconductor film, and the thirdsemiconductor film; forming a first conductive film and a secondconductive film selectively over the first semiconductor film and thesecond semiconductor film, respectively, with the first insulating filminterposed therebetween; removing the first insulating film which isformed over the third semiconductor film; forming a second insulatingfilm to cover the first conductive film, the second conductive film, andthe third semiconductor film; forming a third conductive filmselectively over the first conductive film which is formed over thefirst semiconductor film, with the second insulating film interposedbetween the first conductive film and the third conductive film; forminga fourth conductive film selectively over the third semiconductor filmwith the second insulating film interposed therebetween; doping thefirst semiconductor film with an impurity element with the thirdconductive film serving as a mask, doping the third semiconductor filmwith the impurity element with the fourth conductive film serving as amask, and doping the second semiconductor film with the impurity elementthrough the second conductive film; forming a third insulating film tocover the third conductive film, the fourth conductive film, and thesecond insulating film; and forming a conductive film serving as anantenna over the third insulating film.

A semiconductor device according to another aspect of the presentinvention includes a substrate; a first semiconductor film and a secondsemiconductor film which have island-shaped and formed over thesubstrate; a first insulating film formed over the first semiconductorfilm and the second semiconductor film; a first conductive film and asecond conductive film which are formed over the first semiconductorfilm and the second semiconductor film, respectively, with the firstinsulating film interposed therebetween; a second insulating film formedover the first conductive film and the second conductive film; and athird conductive film formed over the first conductive film with thesecond insulating film interposed therebetween. In the semiconductordevice, the first semiconductor film, the first insulating film, thefirst conductive film, the second insulating film, and the thirdconductive film are stacked to form a nonvolatile memory element; thesecond semiconductor film, the first insulating film, and the secondconductive film are stacked to form a capacitor; and a concentration ofan impurity element contained in a region of the second semiconductorfilm which is under the second conductive film is higher than aconcentration of an impurity element contained in a region of the firstsemiconductor film which is under the first conductive film.

A semiconductor device according to another aspect of the presentinvention includes a substrate; a first semiconductor film, a secondsemiconductor film, and a third semiconductor film which areisland-shaped and formed over the substrate; a first insulating filmformed over the first semiconductor film and the second semiconductorfilm; a first conductive film and a second conductive film which areformed over the first semiconductor film and the second semiconductorfilm, respectively, with the first insulating film interposedtherebetween; a second insulating film formed over the first conductivefilm, the second conductive film, and the third semiconductor film; athird conductive film formed over the first conductive film with thesecond insulating film interposed therebetween; and a fourth conductivefilm formed over the third semiconductor film with the second insulatingfilm interposed therebetween. In the semiconductor device, the firstsemiconductor film, the first insulating film, the first conductivefilm, the second insulating film, and the third conductive film arestacked to form a nonvolatile memory element; the second semiconductorfilm, the first insulating film, and the second conductive film arestacked to form a capacitor; the third semiconductor film, the secondinsulating film, and the fourth conductive film are stacked to form athin film transistor; and a concentration of an impurity elementcontained in a region of the second semiconductor film which is underthe second conductive film is higher than a concentration of an impurityelement contained in a region of the first semiconductor film which isunder the first conductive film, and is higher than a concentration ofan impurity element contained in a region of the third semiconductorfilm which is under the fourth conductive film.

A semiconductor device according to another aspect of the presentinvention includes a substrate; a first semiconductor film, a secondsemiconductor film, and a third semiconductor film which areisland-shaped and formed over the substrate; a first insulating filmformed over the first semiconductor film and the second semiconductorfilm; a first conductive film and a second conductive film which areformed over the first semiconductor film and the second semiconductorfilm, respectively, with the first insulating film interposedtherebetween; a second insulating film formed over the first conductivefilm, the second conductive film, and the third semiconductor film; athird conductive film formed over the first conductive film with thesecond insulating film interposed therebetween; a fourth conductive filmformed over the third semiconductor film with the second insulating filminterposed therebetween; a third insulating film formed to cover thethird conductive film, the fourth conductive film, and the secondinsulating film; and a conductive film serving as an antenna which isformed over the third insulating film. In the semiconductor device, thefirst semiconductor film, the first insulating film, the firstconductive film, the second insulating film, and the third conductivefilm are stacked to form a nonvolatile memory element; the secondsemiconductor film, the first insulating film, and the second conductivefilm are stacked to form a capacitor; the third semiconductor film, thesecond insulating film, and the fourth conductive film are stacked toform a thin film transistor; and a concentration of an impurity elementcontained in a region of the second semiconductor film which is underthe second conductive film is higher than a concentration of an impurityelement contained in a region of the first semiconductor film which isunder the first conductive film, and is higher than a concentration ofan impurity element contained in a region of the third semiconductorfilm which is under the fourth conductive film.

According to the present invention, manufacturing steps and cost can bereduced because, in doping a semiconductor film which is included in atransistor or a memory element with an impurity element, a semiconductorfilm which serves as one electrode of a capacitor is also doped with theimpurity element through the other electrode of the capacitor. Further,capacitance per unit area is increased and an area of an element can bereduced by manufacturing an insulating film included in the capacitor tohave approximately the same thickness as an insulating film which canserve as a tunnel insulating film of the memory element.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1F are diagrams showing an example of a method ofmanufacturing a semiconductor device of the present invention;

FIGS. 2A to 2D are diagrams showing an example of a method ofmanufacturing a semiconductor device of the present invention;

FIGS. 3A to 3D are diagrams showing an example of a method ofmanufacturing a semiconductor device of the present invention;

FIGS. 4A to 4C are diagrams showing an example of a method ofmanufacturing a semiconductor device of the present invention;

FIGS. 5A and 5B are diagrams showing an example of a method ofmanufacturing a semiconductor device of the present invention;

FIGS. 6A to 6C are diagrams showing an example of a method ofmanufacturing a semiconductor device of the present invention;

FIGS. 7A and 7B are diagrams showing an example of a method ofmanufacturing a semiconductor device of the present invention;

FIGS. 8A to 8C are diagrams showing an example of a method ofmanufacturing a semiconductor device of the present invention;

FIGS. 9A and 9B are diagrams showing an example of a method ofmanufacturing a semiconductor device of the present invention;

FIG. 10 is a diagram showing a method of manufacturing a semiconductordevice of the present invention;

FIGS. 11A to 11C are diagrams showing an example of usage of asemiconductor device of the present invention; and

FIGS. 12A to 12H are diagrams showing an example of usage of asemiconductor device of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiment modes of the present invention are describedwith reference to the drawings. Note that the present invention can becarried out in many different modes, and it will be readily appreciatedby those skilled in the art that modes and details can be modified invarious ways without departing from the sprit and scope of the presentinvention. Accordingly, the present invention should not be construed asbeing limited to the description of the embodiment modes. Note that inthe drawings for illustrating the embodiment modes, common portions orpotions having similar functions hold the same reference numerals andrepeated description there of is omitted.

Embodiment Mode 1

In this embodiment mode, a method of manufacturing a semiconductordevice of the present invention and a structure of the semiconductordevice obtained by the manufacturing method are described with referenceto the drawings.

A method of manufacturing a semiconductor device in this embodiment modeis described with reference to FIGS. 1A to 2D.

First, an insulating film 102 is formed on the substrate 101 and anamorphous semiconductor film 103 (e.g., a film containing amorphoussilicon) is formed over the insulating film 102 (see FIG. 1A). Theinsulating film 102 and the amorphous semiconductor film 103 can beformed successively in a vacuum. When the insulating film 102 and theamorphous semiconductor film 103 are formed successively, they are notexposed to atmosphere, so that contamination by impurity elements can beprevented.

As the substrate 101, a glass substrate, a quartz substrate, a metalsubstrate, a stainless steel substrate, a plastic substrate which canwithstand the treatment temperature of the process described here, orthe like can be used. When such a substrate is used, the area and theshape thereof are not particularly limited. For example, when arectangular substrate having one meter or longer on one side is used,productivity can be drastically improved. This is a great advantage overthe case of using a circular silicon substrate and even in the case offorming a large integrated circuit portion, the cost can be low comparedto the case of using a silicon substrate.

The insulating film 102 is a single layer or stacked-layers whichincludes a film containing oxide of silicon or nitride of silicon (e.g.,a silicon oxide (SiO_(x)) film, a silicon oxynitride (SiO_(x)N_(y))(where x>y) film, a silicon nitride (SiN_(x)) film, or a silicon nitrideoxide (SiN_(x)O_(y)) (where x>y) film) formed by a sputtering method, aplasma CVD method, or the like. When the insulating film which serves asa base has a two-layer structure, a silicon nitride oxide film and asilicon oxynitride film may be formed as a first layer and a secondlayer, respectively. When the insulating film which serves as a base hasa three-layer structure, a silicon oxide film, a silicon nitride oxidefilm, and a silicon oxynitride film may be formed as a first layer, asecond layer, and a third layer, respectively. Alternatively, a siliconoxynitride film, a silicon nitride oxide film, and a silicon oxynitridefilm may be formed as a first layer, a second layer, and a third layer,respectively. The insulating film which serves as a base functions as ablocking film which prevents an impurity from the substrate 101.

The semiconductor film 103 is formed to have a thickness of 25 to 200 nm(preferably, 30 to 150 nm) by a sputtering method, an LPCVD method, aplasma CVD method, or the like. As the semiconductor film 103, anamorphous silicon film is formed hereinafter.

Then, the amorphous semiconductor film 103 is crystallized by laserlight irradiation. Note that the amorphous semiconductor film 103 may becrystallized by a method in which laser light irradiation is combinedwith a thermal crystallization method using an RTA or an annealingfurnace or thermal crystallization using a metal element which promotescrystallization. Then, thus obtained crystalline semiconductor film isetched into desired shapes to form crystalline semiconductor films 103 aand 103 b. Insulating films 104 a and 104 b are formed to cover thecrystalline semiconductor films 103 a and 103 b, respectively (see FIG.1B).

An example of a manufacturing process of the crystalline semiconductorfilms 103 a and 103 b is briefly explained below. First, the amorphoussemiconductor film 103 (e.g., an amorphous silicon film) is formed by aplasma CVD method to have a thickness of 50 to 60 nm. Then, theamorphous semiconductor film is doped with nickel, which is a metalelement for promoting crystallization, and dehydrogenation treatment (at500° C., for one hour) and thermal crystallization treatment (at 550°C., for four hours) are performed, thus, a crystalline semiconductorfilm is formed. After that, the crystalline semiconductor film isirradiated with laser light from a laser and is processed using aphotolithography method to form the crystalline semiconductor films 103a and 103 b. Note that the amorphous semiconductor film may becrystallized only by laser light irradiation without thermalcrystallization using a metal element for promoting crystallization.

Each of the insulating films 104 a and 104 b is a single layer orstacked-layers which includes a film containing oxide of silicon ornitride of silicon formed by a CVD method, a sputtering method, or thelike. In specific, a single layer or stacked-layers which includes anyof a silicon oxide film, a silicon oxynitride film, a silicon nitridefilm, and a silicon nitride oxide film are formed.

Alternatively, the insulating films 104 a and 104 b may be formed byoxidizing or nitriding the surfaces of the crystalline semiconductorfilms 103 a and 103 b by performing a plasma treatment. For example, theinsulating films 104 a and 104 b are formed by performing a plasmatreatment in which a mixed gas containing a rare gas such as He, Ar, Kr,or Xe and oxygen, nitrogen oxide, ammonia, nitrogen, or hydrogen isadded. When excitation of the plasma is conducted by introduction of amicrowave, plasma with a low electron temperature and a high density canbe generated. Surfaces of the semiconductor films can be oxidized ornitrided by oxygen radicals (which may include OH radicals) or nitrogenradicals (which may include NH radicals) generated by such high-densityplasma.

By the treatment using such high-density plasma, an insulating film isformed over the crystalline semiconductor film to have a thickness of 1to 20 nm, typically 5 to 10 nm. Since the reaction in this case is asolid-phase reaction, the interface state density between the insulatingfilm and the crystalline semiconductor film can be quite low. Since suchhigh-density plasma treatment directly oxidizes (or nitrides) asemiconductor film (crystalline silicon or polycrystalline silicon),variation in thickness of the formed insulating film can be quite small.Further, crystal grain boundaries of crystalline silicon are notexcessively oxidized, which makes a very favorable condition. In otherwords, by solid-phase oxidation of a surface of the crystallinesemiconductor film by the high-density plasma treatment described here,an insulating film with good uniformity and low interface state densitycan be formed without excessive oxidation reaction at crystal grainboundaries.

As the insulating films 104 a and 104 b, an insulating film formed byhigh-density plasma treatment may only be used, or an insulating film ofsilicon oxide, silicon oxynitride, silicon nitride, or the like may beadditionally deposited by a CVD method utilizing a plasma or thermalreaction and may be stacked. In any case, transistors includinginsulating films which are formed by high-density plasma as a part ofgate insulating films or as the gate insulating films can have littlevariation in characteristics.

Then, a conductive film 105 is formed over the insulating films 104 aand 104 b (see FIG. 1C). The conductive film 105 can be, for example, afilm including an element selected from tungsten (W), tantalum (Ta),titanium (Ti), molybdenum (Mo), chromium (Cr), and silicon (Si); a filmincluding nitride of such an element (typically, a tungsten nitridefilm, a tantalum nitride film, or a titanium nitride film); an alloyfilm in which such elements are combined (typically, a Mo—W alloy or aMo—Ta alloy); or a silicide film of such an element (typically, atungsten silicide film, a titanium silicide film, or a nickel silicidefilm) can be used. An impurity such as phosphorus or boron may be addedto a silicon film. The conductive layer may be a single layer or astacked-layer including two or three layers. The conductive layer isformed by a sputtering method or a CVD method.

Then, a resist 106 is formed selectively over the conductive film 105.The conductive film 105 is selectively etched with the resist 106serving as a mask so that a conductive film 105 a and a conductive film105 b are left over the crystalline semiconductor film 103 a and thecrystalline semiconductor film 103 b, respectively. Then, thecrystalline semiconductor films 103 a and 103 b is doped an impurityelement with the resist 106 serving as a mask to form impurity regions107 in the crystalline semiconductor films 103 a and 103 b (see FIG.1D).

An impurity element which is used for the doping is either an n-typeimpurity element or a p-type impurity element. As an n-type impurityelement, phosphorus (P), arsenic (As), or the like can be used. As ap-type impurity element, boron (B), aluminium (Al), gallium (Ga), or thelike can be used. Here, the case where the crystalline semiconductorfilms 103 a and 103 b is doped with phosphorus (P) to form the impurityregions 107 which are n-type impurity regions is described.

The conductive film 105 a serves as a floating gate in a memory elementwhich is formed later, while the conductive film 105 b serves as anelectrode in a capacitor which is formed later.

Then, after the resist 106 is removed, an insulating film 108 is formedto cover the conductive films 105 a and 105 b (see FIG. 1E). Theinsulating film 108 is a single layer or stacked-layers including a filmwhich includes oxide of silicon or nitride of silicon (e.g., a siliconoxide film, a silicon oxynitride film, a silicon nitride film, or asilicon nitride oxide film) formed by a sputtering method, a plasma CVDmethod, or the like. For example, the insulating film 108 can have astructure in which a silicon oxynitride film, a silicon nitride film,and a silicon oxynitride film are stacked in that order.

Then, a conductive film 109 is formed over the insulating film 108 (seeFIG. 1F).

The conductive film 109 can be, for example, a film including an elementselected from tantalum (Ta), tungsten (W), titanium (Ti), molybdenum(Mo), aluminium (Al), copper (Cu), chromium (Cr), and niobium (Nb); afilm including nitride of such an element (typically, a tantalum nitridefilm, a tungsten nitride film, or a titanium nitride film); an alloyfilm in which such elements are combined (typically, a Mo—W alloy or aMo—Ta alloy); or a silicide film of such an element (typically, atungsten silicide film, a titanium silicide film, or a nickel silicidefilm) can be used. The conductive film 109 may have a structure in whicha plurality of conductive films are stacked. For example, a structuremay be employed in which a tantalum nitride film having a thickness of20 nm to 100 nm and a tungsten film having a thickness of 100 nm to 400nm are stacked in this order. Since tungsten and tantalum nitride havehigh thermal resistance, thermal treatment for thermal activation can beperformed after the conductive film is formed.

Then, a resist 110 is formed selectively over the conductive film 109.The conductive film 109 is selectively etched with the resist 110serving as a mask to leave a conductive film 109 a over the crystallinesemiconductor film 103 a (see FIG. 2A). The conductive film 109 formedover the crystalline semiconductor film 103 b is removed.

Then, after the resist 110 is removed, the crystalline semiconductorfilms 103 a and 103 b are doped with an impurity element with theconductive film 109 a serving as a mask (see FIG. 2B). A part of thecrystalline semiconductor film 103 a which does not overlap with theconductive film 109 a is doped with the impurity element to formimpurity regions 111 a. Note that LDD regions 133 which includelow-concentrated impurity element are also formed. The entire part ofthe crystalline semiconductor film 103 b is doped with the impurityelement through the conductive film 105 b to form impurity regions 112 aand an impurity region 112 b which overlaps with the conductive film 105b. Note that a part of the crystalline semiconductor film 103 a which isunder the conductive film 105 a is not doped with an impurity element.Accordingly, a concentration of an impurity element which is containedin a region of the crystalline semiconductor film 103 b which is underthe conductive film 105 b is higher than a concentration of an impurityelement which is contained in a region of the crystalline semiconductorfilm 103 a which is under the conductive film 105 a.

An impurity element which is used for the doping is either an n-typeimpurity element or a p-type impurity element. As an n-type impurityelement, phosphorus (P), arsenic (As), or the like can be used. As ap-type impurity element, boron (B), aluminium (Al), gallium (Ga), or thelike can be used. Here, the case where the crystalline semiconductorfilms 103 a and 103 b are doped with phosphorus (P) at highconcentration to form the impurity regions 111 a, 112 a, and 112 b whichare n-type impurity regions is described. In addition, a concentrationof the impurity element in the impurity regions 111 a, 112 a, and 112 bis higher than a concentration of the impurity element in the impurityregion 107 s formed in FIG. 1D. Needless to say, the crystallinesemiconductor films may be doped with boron (B) to form p-type impurityregions.

Note that when the crystalline semiconductor film 103 b is doped with animpurity element through the conductive film 105 b, it is desirable thatthe insulating film 104 b, the conductive film 105 b, and the insulatingfilm 108, which are formed over the crystalline semiconductor film 103b, are thin films and that the impurity element is added at a highlyaccelerated speed. In specific, the insulating film 104 b having athickness of 5 nm to 15 nm, the conductive film 105 b having a thicknessof 10 nm to 50 nm, and the insulating film 108 having a thickness of 20nm to 60 nm are formed and the impurity element is added by a dopingmethod at an accelerating voltage of 30 kV to 80 kV. Preferably, theinsulating film 104 b having a thickness of 8 nm to 10 nm, theconductive film 105 b having a thickness of 20 nm to 40 nm, and theinsulating film 108 having a thickness of 30 nm to 40 nm are formed andan impurity element is added by a doping method at an acceleratingvoltage of 40 kV to 50 kV. If an accelerating voltage is too high, theinsulating film 104 b may be damaged. When the foregoing condition isemployed, the part of the semiconductor film 103 b which overlaps withthe conductive film 105 b can be doped with an impurity element whiledamage on the insulating film 104 b is reduced.

As in the above-described manner, in a process of forming an impurityregion which can serve as a source region or a drain region in asemiconductor film which is included in a transistor-type memoryelement, a semiconductor film which is included in a capacitor is alsodoped with the impurity element; thus, reduction in the number ofmanufacturing steps and reduction in cost can be achieved.

Then, an insulating film 113 is formed to cover the conductive film 109a and the insulating film 108 (see FIG. 2C). The insulating film 113 isa single layer or stacked-layers of inorganic material such as oxide ofsilicon or nitride of silicon; an organic material such as polyimide,polyamide, benzocyclobutene, acryl, or epoxy; a siloxane material; orthe like and is formed by a CVD method, a sputtering method, an SOGmethod, a droplet discharge method, a screen printing method, or thelike. For example, the insulating film 113 can have a stacked-layerstructure including two layers of a silicon nitride oxide film and asilicon oxynitride film. Note that a siloxane material is a materialhaving a Si—O—Si bond. Siloxane has a skeleton structure including abond of silicon (Si) and oxygen (O). Siloxane includes an organic groupcontaining at least hydrogen (such as an alkyl group or aromatichydrocarbon) as a substituent. Alternatively, siloxane may include afluoro group as a substituent. Further alternatively, siloxane mayinclude both an organic group containing at least hydrogen and a fluorogroup as a substituent.

Note that before or after forming the insulating film 113, thermaltreatment may be performed for recovering crystallinity of thesemiconductor film, activating an impurity element which is added to thesemiconductor film, or hydrogenating the semiconductor film. The thermaltreatment can employ a thermal anneal or laser anneal method, an RTAmethod, or the like.

Then, conductive films 114 which are electrically connected to theimpurity regions 111 a in the crystalline semiconductor film 103 a andthe impurity regions 112 a in the crystalline semiconductor film 103 bare formed (see FIG. 2D). Here, opening portions are formed in theinsulating films 104 a, 104 b, 108, and 113 to expose parts of theimpurity regions 111 a in the crystalline semiconductor film 103 a andthe impurity regions 112 a in the crystalline semiconductor film 103 b.The conductive films 114 are formed in the opening portions.

The conductive film 114 is a single layer or stacked-layers whichincludes an element selected from aluminium (Al), tungsten (W), titanium(Ti), tantalum (Ta), molybdenum (Mo), nickel (Ni), platinum (Pt), copper(Cu), gold (Au), silver (Ag), manganese (Mn), neodymium (Nd), carbon(C), and silicon (Si); or an alloy material or a compound material whichcontains such an element as its main component; and is formed by a CVDmethod, a sputtering method, or the like. An alloy material containingaluminium as its main component refers to, for example, a materialcontaining aluminum as its main component which also contains nickel,and an alloy material containing aluminum as its main component whichalso contains nickel and either or both of carbon and silicon. Theconductive films 114 preferably have, for example, a stacked-layerstructure including a barrier film, an aluminum-silicon (Al—Si) film,and a barrier film, or a stacked-layer structure including a barrierfilm, an aluminum-silicon (Al—Si) film, a titanium nitride film, and abarrier film. Note that a barrier film refers to a thin film includingtitanium, nitride of titanium, molybdenum, or nitride of molybdenum.Aluminum and aluminum silicon, which have low resistance values and areinexpensive, are the optimal materials for forming the conductive films114. When barrier layers are provided as an upper layer and a lowerlayer, generation of hillocks of aluminum or aluminum silicon can beprevented. Further, when a barrier film contains titanium which is anelement having a high reducing property, even if there is a thin naturaloxide film formed on the crystalline semiconductor film, the naturaloxide film can be reduced, and a favorable contact between theconductive film 114 and the crystalline semiconductor film can beobtained.

As the foregoing process, a semiconductor device including the memoryelement 120 and the capacitor 121 can be obtained.

In the semiconductor device described in this embodiment mode, thememory element 120 includes the insulating film 104 a, which can serveas a tunnel insulating film 104 a, the conductive film 105 a, which canserve as a floating gate, the insulating film 108, which can serve as aninterlayer film between the conductive film 105 a and the conductivefilm 109 a, and the conductive film 109 a, which can serve as a gateelectrode.

The capacitor 121 has a structure in which the insulating film 104 b isprovided between the crystalline semiconductor film 103 b and theconductive film 105 b which can serve as electrodes. The conductive film105 b is formed of the same material as the conductive film 105 a, whichcan serve as a floating gate of the memory element 120, and theinsulating film 104 b is formed of the same material as the insulatingfilm 104 a, which can serve as a tunnel insulating film of the memoryelement 120. The insulating film 104 b of the capacitor 121 is formed ofthe same material as the insulating film 104 a, which can serve as atunnel insulating film of the memory element 120, so that the thicknessof the insulating film included in the capacitor can be small; thus thearea of the capacitor can be reduced.

When the memory element 120 and the capacitor 121 are formed in the sameprocess as described above, simplification in manufacturing process canbe achieved and cost reduction can be realized. In particular, since thesemiconductor film which serves as one electrode of the capacitor 121 isdoped with an impurity element through the conductive film 105 b in thisembodiment mode, a step of doping only the crystalline semiconductorfilm 103 b with an impurity element selectively before forming theconductive film 105 b can be omitted; therefore, the manufacturingprocess can be simplified.

Note that while an example in which a thin film transistor (TFT)-typememory element or a capacitor is used as a memory element in thisembodiment mode, the present invention is not limited thereto. Forexample, a structure may be employed in which a semiconductor film whichis formed using an SOI substrate is used as an electrode of a memoryelement.

This embodiment mode can be implemented by being combined with astructure of a semiconductor device or a method of manufacturing asemiconductor device which is described in another embodiment mode inthis specification.

Embodiment Mode 2

In this embodiment mode, a method of manufacturing a semiconductordevice which is different from the method described in the foregoingembodiment mode and a structure of a semiconductor device obtained bythe method are described with reference to the drawings. In specific, amethod of manufacturing a memory element, a capacitor, and a transistorin the same process, and a structure of a semiconductor device obtainedby the method are described with reference to the drawings.

A method of manufacturing a semiconductor device in this embodiment modeis described with reference to FIGS. 3A to 5B.

First, the crystalline semiconductor films 103 a, 103 b, 203 a, and 203b, which are island-shaped and formed over one surface of the substrate101 with insulating film 102 interposed therebetween (see FIG. 3A). Notethat a memory element which is formed later has the crystallinesemiconductor film 103 a, a capacitor which is formed later has thecrystalline semiconductor film 103 b, and a thin film transistor whichis formed later has the crystalline semiconductor films 203 a and 203 b.

Then, the insulating films 104 a, 104 b, 204 a, and 204 b are formed tocover the crystalline semiconductor films 103 a, 103 b, 203 a, and 203b, respectively. Then, the conductive film 105 is formed to cover theinsulating films 104 a, 104 b, 204 a, and 204 b (see FIG. 3B).

Further, the crystalline semiconductor films 103 a, 203 a, and 203 b maybe doped with an impurity element at low concentration in advance, inorder to control a threshold value or the like. In this case, regionswhich serve as channel formation regions in the crystallinesemiconductor films 103 a, 203 a, and 203 b later is also doped with theimpurity element. The impurity element can be either an impurity elementimparting n-type conductivity or an impurity element imparting p-typeconductivity. As an impurity element imparting n-type conductivity,phosphorus (P), arsenic (As), or the like can be used. As an impurityelement imparting p-type conductivity, boron (B), aluminium (Al),gallium (Ga), or the like can be used. Here, the entire part of thecrystalline semiconductor films 103 a, 203 a, and 203 b is doped withboron (B) as the impurity element in advance to contain boron (B) at aconcentration of 5×10¹⁵ to 5×10¹⁷/cm³.

Then, after removing a selected portion of the conductive film 105 whichis formed above the crystalline semiconductor films 203 a and 203 b, theinsulating film 204 a and the insulating film 204 b are removed (seeFIG. 3C). Note that the conductive film 105 is left above thecrystalline semiconductor films 103 a and 103 b.

Then, the resists 106 are formed selectively over the conductive film105 which is left and to cover the crystalline semiconductor films 203 aand 203 b. After that, the conductive film 105 which is left is furtheretched selectively with the resists 106 serving as a mask so that theconductive films 105 a and 105 b are left over the crystallinesemiconductor film 103 a and 103 b, respectively. Then, the crystallinesemiconductor films 103 a and 103 b are doped with an impurity elementwith the resist 106 serving as a mask to form the impurity regions 107in the crystalline semiconductor films 103 a and 103 b (see FIG. 3D).

An impurity element which is used for the doping is either an n-typeimpurity element or a p-type impurity element. As an n-type impurityelement, phosphorus (P), arsenic (As), or the like can be used. As ap-type impurity element, boron (B), aluminium (Al), gallium (Ga), or thelike can be used. Here, the case where the crystalline semiconductorfilms 103 a and 103 b are doped with phosphorus (P) to form the impurityregions 107 is described.

Next, the resist 106 is removed, and then the insulating film 108 isformed to cover the crystalline semiconductor films 203 a and 203 b, andthe conductive films 105 a and 105 b. After that, the conductive film109 is formed over the insulating film 108 (see FIG. 4A).

Then, the resist 110 is formed selectively over the conductive film 109.The conductive film 109 is selectively etched with the resist 110serving as a mask to leave conductive films 109 a, 209 a, and 209 b overthe crystalline semiconductor films 103 a, 203 a, and 203 b,respectively (see FIG. 4A). The conductive film 109 formed over thecrystalline semiconductor film 103 b is removed.

Then, after the resist 110 is removed, a resist 210 a is formed to coverthe crystalline semiconductor films 103 a and 203 b. The crystallinesemiconductor films 203 a and 103 b is doped with an impurity elementwith the resist 210 a and the conductive film 209 a serving as a mask(see FIG. 4C). A region of the crystalline semiconductor film 203 awhich does not overlap with the conductive film 209 a is doped with theimpurity element to form impurity regions 211. The entire part of thecrystalline semiconductor film 103 b is doped with an impurity elementthrough the conductive film 105 b to form impurity regions 112 a and animpurity region 112 b which overlaps with the conductive film 105 b.

An impurity element which is used for the doping is either an n-typeimpurity element or a p-type impurity element. Here, the case isdescribed where the crystalline semiconductor films 203 a and 103 b isdoped with boron (B), which is a light element and is a p-type impurityelement, at high concentration to form p-type impurity regions 211, 112a, and 112 b. When the crystalline semiconductor film 103 b is dopedwith an impurity element through the insulating film 108, the conductivefilm 105, and the insulating film 104 b, the damage of the insulatingfilm 104 b can be reduced by using a light element like boron (B) as theimpurity element.

Then, after the resist 210 a is removed, a resist 210 b is formed tocover the crystalline semiconductor films 103 b and 203 a. Thecrystalline semiconductor films 103 a and 203 b are doped with animpurity element with the resist 210 b and conductive films 109 and 209b serving as a mask (see FIG. 5A). A region of the crystallinesemiconductor film 103 a which is not overlapped with the conductivefilm 109 a is doped with the impurity element to form impurity regions111. A region of the crystalline semiconductor film 203 b which does notoverlap with the conductive film 209 b is doped with the impurityelement to form impurity regions 212. Note that doping with an impurityelement to the crystalline semiconductor film 103 b is not necessarilyperformed at the step illustrated in FIG. 4C. The doping may beperformed at the step illustrated in FIG. 5A and at the same time asdoping the crystalline semiconductor films 103 b and 203 a with animpurity element. Accordingly, a concentration of an impurity elementwhich is contained in a region of the crystalline semiconductor film 103b which is under the conductive film 105 b is higher than aconcentration of an impurity element which is contained in a region ofthe crystalline semiconductor film 103 a which is under the conductivefilm 105 a, higher than a concentration of an impurity element which iscontained in a region of the crystalline semiconductor film 203 a whichis under the conductive film 209 a, and higher than a concentration ofan impurity element which is contained in a region of the crystallinesemiconductor film 203 b which is under the conductive film 209 b.

An impurity element which is used for the doping is either an n-typeimpurity element or a p-type impurity element. Here, the case where thecrystalline semiconductor films 103 a and 203 b are doped withphosphorus (P) at high concentration to form the n-type impurity regions111 and 212 is described.

Then, the insulating film 113 is formed to cover the conductive films109 a, 209 a, and 209 b and the insulating film 108. After that,conductive films 114 which are electrically connected to the impurityregions 111 in the crystalline semiconductor film 103 a, the impurityregions 112 a in the crystalline semiconductor film 103 b, the impurityregions 211 in the crystalline semiconductor film 203 a, and theimpurity regions 212 in the crystalline semiconductor film 203 b areformed (see FIG. 5B).

By the foregoing process, a semiconductor device including the memoryelement 120, the capacitor 121, and the thin film transistors 220 and221 can be obtained.

Note that while this embodiment mode describes an example in which athin film transistor is used as a transistor, a type of a transistor isnot limited thereto and various types of transistors can be employed.That is, there is no limitation on types of transistor which can beused. Accordingly, a transistors which can be employed is not limited toa thin film transistor (TFT) using a non-single crystal semiconductorfilm typified by amorphous silicon or polycrystal silicon, and atransistor formed using a semiconductor substrate or an SOI substrate, aMOS transistor, a junction transistor, a bipolar transistor, atransistor using a compound semiconductor such as ZnO or a-InGaZnO, atransistor using an organic semiconductor or carbon nanotube, or thelike can be used. Note that a non-single crystal semiconductor film maycontain hydrogen or halogen.

In addition, a transistor can have various structures without limitationto a certain structure. For example, a multigate structure which has twoor more gates may be employed. With a multi-gate structure, off-currentcan be reduced and withstand voltage of the transistor can be increasedso as to improve the reliability, and drain-source current does notgreatly changes even when drain-source voltage changes in a saturationregion so that flat characteristics can be realized. Further, an LDDregion may be provided. With an LDD region, off-current can be reducedand withstand voltage of the transistor can be increased so as toimprove the reliability, and drain-source current does not greatlychange even when drain-source voltage changes in a saturation region sothat flat characteristics can be realized.

This embodiment mode can be implemented by being combined with astructure of a semiconductor device or a method of manufacturing asemiconductor device which is described in another embodiment mode inthis specification.

Embodiment Mode 3

In this embodiment mode, an example of an application of a semiconductordevice described in the foregoing embodiment modes is described.Specifically, examples of an application of the semiconductor devicewhich can input and output data without contact is described withreference to the drawings. A semiconductor device which can input andoutput data without contact is also referred to as an RFID tag, an IDtag, an IC tag, an IC chip, an RF tag, a wireless tag, an electronictag, or a wireless chip depending on the usage mode.

A semiconductor device 80 has a function of communicating data withoutcontact, and includes a high frequency circuit 81, a power sourcecircuit 82, a reset circuit 83, a clock generation circuit 84, a datademodulation circuit 85, a data modulation circuit 86, a control circuit87 which controls another circuit, a storage circuit 88, and an antenna89 (see FIG. 11A). The high frequency circuit 81 is a circuit whichreceives a signal from the antenna 89, and receives a signal from thedata modulation circuit 86 and outputs the signal through the antenna89. The power source circuit 82 is a circuit which generates a powersource potential from the received signal. The reset circuit 83 is acircuit which generates a reset signal. The clock generation circuit 84is a circuit which generates various clock signals based on the receivedsignal inputted from the antenna 89. The data demodulation circuit 85 isa circuit which demodulates the received signal and outputs the signalto the control circuit 87. The data modulation circuit 86 is a circuitwhich modulates the signal received from the control circuit 87. In thecontrol circuit 87, a code extraction circuit 91, a code determinationcircuit 92, a CRC determination circuit 93, and an output unit circuit94 are included, for example. Note that the code extraction circuit 91is a circuit which separately extracts a plurality of codes included inan instruction transmitted to the control circuit 87. The codedetermination circuit 92 is a circuit which compares the extracted codeand a reference code to determine the content of the instruction. TheCRC circuit is a circuit which detects the presence or absence of atransmission error or the like based on the determined code.

Next, an example of operation of the foregoing semiconductor device isdescribed. First, a radio signal is received by the antenna 89. Theradio signal is transmitted to the power source circuit 82 via the highfrequency circuit 81, and a high power source potential (hereinafterreferred to as VDD) is generated. The VDD is supplied to each circuitincluded in the semiconductor device 80. In addition, a signaltransmitted to the data demodulation circuit 85 via the high frequencycircuit 81 is demodulated (hereinafter, such a signal is referred to asa demodulated signal). Further, the demodulated signal and a signalwhich has passed the high frequency circuit 81 and the reset circuit 83or the clock generation circuit 84 are transmitted to the controlcircuit 87. The signal transmitted to the control circuit 87 is analyzedby the code extraction circuit 91, the code determination circuit 92,the CRC determination circuit 93, and the like. Then, in accordance withthe analyzed signal, information of the semiconductor device which isstored in the storage circuit 88 is outputted. The outputted informationof the semiconductor device is encoded by passing through the outputunit circuit 94. Furthermore, the encoded information of thesemiconductor device 80 is passed through the data modulation circuit 86and transmitted by the antenna 89 as a radio signal. Note that a lowpower source potential (hereinafter, referred to as VSS) is common amonga plurality of circuits included in the semiconductor device 80, and VSScan be GND.

In this manner, a signal is transmitted from the reader/writer to thesemiconductor device 80 and a signal transmitted from the semiconductordevice 80 is received by the reader/writer, thus, the data of thesemiconductor device can be read.

The semiconductor device 80 may be either a type where no power supply(battery) is built-in but electromagnetic waves are used to supply apower supply voltage to each circuit, or a type where bothelectromagnetic waves and a power supply (battery) are used to generatea power supply voltage for each circuit.

By applying a manufacturing method described in any of the foregoingembodiment modes to the high frequency circuit 81, the power sourcecircuit 82, the reset circuit 83, the clock generation circuit 84, thedata demodulation circuit 85, the data modulation circuit 86, thecontrol circuit 87, and the storage circuit 88, a semiconductor devicecan be obtained at low cost.

Next, an example of a usage mode of a semiconductor device which caninput and output data without contact is described. A reader/writer 3200is attached to a side face of a portable terminal including a displayportion 3210, and a semiconductor device 3230 is attached to a side faceof an article 3220 (see FIG. 11B). When the reader/writer 3200 is putclose to the semiconductor device 3230 included in the article 3220,information of the article 3220, such as a raw material, the place oforigin, an inspection result in each production process, the history ofdistribution, or an explanation of the article, is displayed on thedisplay portion 3210. Furthermore, the product 3260 can be inspectedwhile when a product 3260 is transported by a conveyor belt, using areader/writer 3240 and a semiconductor device 3250 attached to theproduct 3260 (see FIG. 11C). Thus, by utilizing the semiconductordevices for systems, information can be acquired easily, and a higherfunction and higher added value can be realized.

As a signal transmission method in the foregoing semiconductor devicewhich can input and output data without contact, an electromagneticcoupling method, an electromagnetic induction method, a microwavemethod, or the like can be used. A transmission method may beappropriately selected by a practitioner in consideration of an intendeduse, and an optimum antenna may be provided in accordance with thetransmission method.

In the case of employing, for example, an electromagnetic couplingmethod or an electromagnetic induction method (e.g., a 13.56 MHz band)as a signal transmission method of the semiconductor device,electromagnetic induction caused by a change in magnetic field densityis used. Therefore, the conductive film serving as an antenna is formedinto an annular shape (e.g., a loop antenna) or a spiral shape (e.g., aspiral antenna).

In the case of employing, for example, a microwave method (for example,an UHF band (860 to 960 MHz band), a 2.45 GHz band, or the like) as asignal transmission method of the semiconductor device, the shape suchas the length of the conductive film serving as an antenna may beappropriately set in consideration of a wavelength of an electromagneticwave which is used for signal transmission. For example, the conductivefilm serving as an antenna can be formed into a linear shape (e.g., adipole antenna), a flat shape (e.g., a patch antenna), or a ribbon-likeshape. In addition, the shape of the conductive film serving as anantenna is not limited to a linear shape, and the conductive filmserving as an antenna may be formed in a curved-line shape, a meandershape, or a combination thereof, in consideration of a wavelength of anelectromagnetic wave.

The conductive film serving as an antenna is formed of a conductivematerial by a CVD method, a sputtering method, a printing method such asscreen printing or gravure printing, a droplet discharge method, adispenser method, a plating method, or the like. The conductive film isformed to have a single-layer structure or a stacked-layer structurewhich includes an element selected from aluminum (Al), titanium (Ti),silver (Ag), copper (Cu), gold (Au), platinum (Pt), nickel (Ni),palladium (Pd), tantalum (Ta), and molybdenum (Mo) or an alloy materialor a compound material containing such an element as its main component.

For example, in the case of forming a conductive film serving as anantenna by using a screen printing method, the conductive film can beformed by selectively printing a conductive paste in which conductiveparticles each having a grain size of several nanometers to several tensof micrometers are dissolved or dispersed in an organic resin. As theconductive particle, a fine particle or a dispersive nanoparticle of oneor more metals of silver (Ag), gold (Au), copper (Cu), nickel (Ni),platinum (Pt), palladium (Pd), tantalum (Ta), molybdenum (Mo), andtitanium (Ti) or silver halide can be used. As the organic resincontained in the conductive paste, one or a plurality of organic resinsserving as a binder, a solvent, a dispersant, or a coating for the metalparticle can be used. Typically, an organic resin such as an epoxy resinor a silicone resin can be used. In formation of the conductive film,baking is preferably performed after the conductive paste is applied.For example, in the case of using fine particles (of which grain size is1 nm to 100 nm inclusive) containing silver as its main component as amaterial of the conductive paste, a conductive film can be obtained byhardening the conductive paste by baking it at a temperature of 150 to300° C. Alternatively, fine particles containing solder or lead-freesolder as its main component may be used; in this case, it is preferableto use a fine particle having a grain size of 20 μm or less. Solder orlead-free solder has an advantage of being low cost.

Note that an applicable range of a flexible semiconductor device is widein addition to the foregoing examples, and the flexible semiconductordevice can be applied to any product as long as it clarifies informationsuch as the history of an object without contact and utilizes theinformation for production, management, or the like. For example, thesemiconductor device can be mounted on bills, coins, securities,certificates, bearer bonds, packing containers, books, recording media,personal belongings, vehicles, food, clothing, health products,commodities, medicine, electronic appliances, and the like. Examples ofthem are described with reference to FIGS. 12A to 12H.

Bills and coins are money distributed to the market, and include onevalid in a certain area (cash voucher), memorial coins, and the like.Securities refer to checks, certificates, promissory notes, and the like(see FIG. 12A). Certificates refer to driver's licenses, certificates ofresidence, and the like (see FIG. 12B). Bearer bonds refer to stamps,rice coupons, various gift certificates, and the like (see FIG. 12C).Packing containers refer to wrapping paper for food containers, plasticbottles, and the like (see FIG. 12D). Books refer to hardbacks,paperbacks, and the like (see FIG. 12E). Recording media refer to DVDsoftware, video tapes, and the like (see FIG. 12F). Vehicles refer towheeled vehicles like bicycles, ships, and the like (see FIG. 12G).Personal belongings refer to bags, glasses, and the like (see FIG. 12H).Food refers to food articles, drink, and the like. Clothing refers toclothes, footwear, and the like. Health products refer to medicalinstruments, health instruments, and the like. Commodities refer tofurniture, lighting equipment, and the like. Medicine refers to medicalproducts, pesticides, and the like. Electronic appliances refer toliquid crystal display devices, EL display devices, television sets (TVreceivers and flat-screen TV receivers), cellular phones, and the like.

Forgery can be prevented by mounting the semiconductor device 80 onbills, coins, securities, certificates, bearer bonds, and the like. Theefficiency of an inspection system, a system used in a rental shop, andthe like can be improved by mounting the semiconductor device 80 onpacking containers, books, recording media, personal belongings, food,commodities, electronic appliances, and the like. Forgery or theft canbe prevented by mounting the semiconductor device 80 on vehicles, healthproducts, medicine, or the like; and wrong use of the medicines can beprevented. The semiconductor device 80 may be provided by, for example,being attached to the surface of an object or embedded in an object. Forexample, the semiconductor device 80 may be embedded in paper of a bookor embedded in an organic resin of a package when the package is made ofan organic resin. When the semiconductor device is provided on paper orthe like, damage on the elements included in the semiconductor devicecan be prevented by providing the semiconductor device which has astructure described in the foregoing embodiment modes.

In this manner, when the semiconductor device is provided for packagingcontainers, storage media, personal belongings, foods, clothing, dailycommodities, electronic appliances, and the like, the efficiency of aninspection system, a rental shop system, and the like can be improved.In addition, when the semiconductor device is provided for vehicles,forgery and theft thereof can be prevented. Further, when thesemiconductor device is implanted in creatures such as animals,identification of the individual creature can be easily carried out. Forexample, when the semiconductor device is implanted in creatures such asdomestic animals, not only the year of birth, sex, breed, and the likebut also health conditions such as body temperature can be easilymanaged.

Note that this embodiment mode can be implemented by being combined witha structure of a semiconductor device or a method of manufacturing thesemiconductor device which is described in another embodiment mode inthis specification. That is, any of the structures of the semiconductordevices, which are described in the foregoing embodiment modes, can beapplied to the semiconductor device described in this embodiment mode.

Embodiment Mode 4

In this embodiment mode, a method of manufacturing the semiconductordevice described in Embodiment Mode 3 which can input and output datawithout contact is described with reference to the drawings. Note thatthis embodiment mode describes a case where a semiconductor device ismanufactured through a step of transferring an element such as a thinfilm transistor which is formed over a supporting substrate (a temporarysubstrate) into a flexible substrate. In addition, this embodiment modedescribes a case where a plurality of chips each including an integratedcircuit portion are provided over one substrate (a supporting substrate)(here, 4 chips in length×3 chips in width) to manufacture a plurality ofsemiconductor devices. In the following description, FIGS. 6A to 7B areschematic top views and FIGS. 8A to 9B are schematic cross-sectionalviews taken along line A₂-B₂ in FIGS. 6A to 7B.

First, a separation layer 301 is formed over one surface of thesubstrate 101, and then the semiconductor films 103 a, 103 b, 203 a, and203 b which are island-shaped are formed with an insulating film 102serving as a base interposed between the separation layer 301 and thesemiconductor films which are island-shaped (see FIGS. 6A and 8A). Notethat in the following steps described below, an integrated circuit andan antenna included in a semiconductor device are formed in each ofregions 320 in FIG. 6A.

Note that, while the separation layer 301 is formed over the entiresurface of the substrate 101 in this step, it is also allowed, ifneeded, that the separation layer 301 is formed over the entire surfaceof the substrate 101, and then processed by a photolithography method tobe provided selectively over the substrate 101. In addition, althoughthe separation layer 301 is formed to be in contact with the substrate101, an insulting film such as a silicon oxide film, a siliconoxynitride film, a silicon nitride film, or a silicon nitride oxide filmmay be formed to be in contact with the substrate 101, if needed, andthen the separation layer 301 may be formed to be in contact with theinsulating film.

The separation layer 301 can be a metal film or stacked-layers whichincludes a metal film and a metal oxide film. As a metal film, a singlelayer or stacked layers are formed using an element selected fromtungsten (W), molybdenum (Mo), titanium (Ti), tantalum (Ta), niobium(Nb), nickel (Ni), cobalt (Co), zirconium (Zr), zinc (Zn), ruthenium(Ru), rhodium (Rh), palladium (Pd), osmium (Os), and iridium (Ir), or analloy material or a compound material containing such an element as amain component. The metal film can be formed by a sputtering method, anyCVD method like a plasma CVD method, or the like. A stacked-layerstructure including a metal film and a metal oxide film can be obtainedby forming the metal film and then applying plasma treatment or thermaltreatment thereon under an oxygen atmosphere or an N₂O atmosphere sothat oxide or oxynitride of the metal film can be formed on a surface ofthe metal film. Alternatively, after the metal film is formed, a surfaceof the metal film may be processed with a solution which is a strongoxidation agent such as ozone water so that oxide or oxynitride of themetal film can be formed on a surface of the metal film.

Then, after steps similar to the steps in FIGS. 3B to 5B, which aredescribed in the foregoing embodiment modes are performed, an insulatingfilm 302 is formed to cover the insulating film 113 and the conductivefilm 114, and then a conductive film 303 serving as an antenna is formedover the insulating film 302 (see FIGS. 6B and 8B).

The insulating film 302 is formed of an inorganic material such as oxideof silicon or nitride of silicon, an organic material such as polyimide,polyamide, benzocyclobutene, acrylic, epoxy, or siloxane by a sputteringmethod, a CVD method, a SOG method, a droplet discharge method, or thelike.

The conductive film 303 is formed of a conductive material by a CVDmethod, a sputtering method, a printing method such as screen printingor gravure printing, a droplet discharge method, a dispenser method, aplating method, or the like. The conductive material is an elementselected from aluminum (Al), titanium (Ti), silver (Ag), copper (Cu),gold (Au), platinum (Pt), nickel (Ni), palladium (Pd), tantalum (Ta),and molybdenum (Mo), or an alloy material or a compound materialcontaining such an element as its main component. The conductive film303 is formed to have a single-layer or stacked-layer structure.

Then, an element formation layer 310 including the thin film transistors220 and 221, the memory element 120, the capacitor 121, the conductivefilm 303 serving as an antenna, and the like is separated from thesubstrate 101.

First, an insulating film 304 is formed to cover the conductive film303, and then laser light irradiation is performed to form an openingportion 305 (see FIGS. 6C and 8C). Then, one surface of the elementformation layer 310 (here, a surface of the insulating film 304) isattached to a first sheet material 306. After that, the elementformation layer 310 is separated from the substrate 101 (see FIG. 9A).As the first sheet material 306, a plastic film such as a hot-melt filmor the like can be used. In the case of separating the first sheetmaterial 306 in a later step, a thermal release tape whose adhesive isreduced when heat is applied thereto can be used as the first sheetmaterial 306.

Note that the surface to be release is wet with an aqueous solution suchas water or ozone water during the separation of the element formationlayer; therefore, breakage of the elements such as the thin filmtransistors 220 and 221, the memory element 120, and the capacitor 121due to static electricity or the like can be prevented. Further, byreusing the substrate 101 from which the element formation layer 310 isseparated, the cost can be reduced.

Next, the second sheet material 307 is attached to the other surface ofthe element formation layer 310 (a surface which is exposed by theseparation from the substrate 101) (see FIGS. 7A and 9B). A flexiblesubstrate such as a plastic substrate can be used as the second sheetmaterial 307.

Then, the element formation layer 310 provided with the second sheetmaterial 307 is cut by dicing, scribing, a laser cutting method, or thelike and thus a plurality of semiconductor devices can be obtained (seeFIGS. 7B and 10). Note that while this embodiment mode describes a casewhere the first sheet material 306 is separated at the same time orafter the second sheet material 307 is attached to the element formationlayer 310, the first sheet material 306 may remain.

This embodiment mode describes the case where elements such as a thinfilm transistor and an antenna are formed over the substrate 101 andthen separated from the substrate 101 to manufacture a flexiblesemiconductor device, but the present invention is not limited to such acase. The flexible semiconductor device can be manufactured over thesubstrate 101 without the separation layer 301.

Note that while this embodiment mode describes an example in which athin film transistor is used as a transistor, a type of a transistor isnot limited thereto and various types of transistors can be employed.That is, there is no limitation on types of transistors which can beused. Accordingly, a transistors which can be employed is not limited toa thin film transistor (TFT) using a non-single crystal semiconductorfilm typified by amorphous silicon or polycrystal silicon, and atransistor formed using a semiconductor substrate or an SOI substrate, aMOS transistor, a junction transistor, a bipolar transistor, atransistor using a compound semiconductor such as ZnO or a-InGaZnO, atransistor using an organic semiconductor or carbon nanotube, or thelike can be used. Note that a non-single crystal semiconductor film maycontain hydrogen or halogen.

In addition, a transistor can have various structures without limitationto a certain structure. For example, a multigate structure which has twoor more gates may be employed. With a multi-gate structure, off-currentcan be reduced and withstand voltage of the transistor can be increasedso as to improve the reliability; and drain-source current does notgreatly changes even when drain-source voltage changes in a saturationregion so that flat characteristics can be realized. Further, an LDDregion may be provided. With an LDD region, off-current can be reducedand withstand voltage of the transistor can be increased so as toimprove the reliability; and drain-source current does not greatlychanges even when drain-source voltage changes in a saturation region sothat flat characteristics can be realized.

This application is based on Japanese Patent Application serial no.2007-046807 filed in Japan Patent Office on Feb. 27, 2007, the entirecontents of which are hereby incorporated by reference.

What is claimed is:
 1. A semiconductor device comprising: a substrate; afirst semiconductor film, a second semiconductor film, and a thirdsemiconductor film which are island-shaped and over the substrate; afirst insulating film over the first semiconductor film and the secondsemiconductor film; a first conductive film and a second conductive filmover the first semiconductor film and the second semiconductor film,respectively, with the first insulating film interposed therebetween; asecond insulating film over the first conductive film, the secondconductive film, and the third semiconductor film; a third conductivefilm over the first conductive film with the second insulating filminterposed therebetween; and a fourth conductive film over the thirdsemiconductor film with the second insulating film interposedtherebetween; wherein the first semiconductor film, the first insulatingfilm, the first conductive film, the second insulating film, and thethird conductive film are stacked to form a nonvolatile memory element;the second semiconductor film, the first insulating film, and the secondconductive film are stacked to form a capacitor; the third semiconductorfilm, the second insulating film, and the fourth conductive film arestacked to form a thin film transistor; and a concentration of animpurity element contained in a region of the second semiconductor filmwhich is under the second conductive film is higher than a concentrationof an impurity element contained in a region of the first semiconductorfilm which is under the first conductive film, and is higher than aconcentration of an impurity element in a region of the thirdsemiconductor film which is under the fourth conductive film.
 2. Asemiconductor device comprising: a substrate; a first semiconductorfilm, a second semiconductor film, and a third semiconductor film whichare island-shaped and over the substrate; a first insulating film overthe first semiconductor film and the second semiconductor film; a firstconductive film and a second conductive film over the firstsemiconductor film and the second semiconductor film, respectively, withthe first insulating film interposed therebetween; a second insulatingfilm over the first conductive film, the second conductive film, and thethird semiconductor film; a third conductive film over the firstconductive film with the second insulating film interposed therebetween;a fourth conductive film over the third semiconductor film with thesecond insulating film interposed therebetween; a third insulating filmcovering the third conductive film, the fourth conductive film, and thesecond insulating film; and a conductive film serving as an antenna overthe third insulating film, wherein the first semiconductor film, thefirst insulating film, the first conductive film, the second insulatingfilm, and the third conductive film are stacked to form a nonvolatilememory element; the second semiconductor film, the first insulatingfilm, and the second conductive film are stacked to form a capacitor;the third semiconductor film, the second insulating film, and the fourthconductive film are stacked to form a thin film transistor; and aconcentration of an impurity element contained in a region of the secondsemiconductor film which is under the second conductive film is higherthan a concentration of an impurity element contained in a region of thefirst semiconductor film which is under the first conductive film, andis higher than a concentration of an impurity element contained in aregion of the third semiconductor film which is under the fourthconductive film.
 3. The semiconductor device according to claim 1,wherein any one of a glass substrate, a plastic substrate, and an SOIsubstrate is used as the substrate.
 4. The semiconductor deviceaccording to claim 2, wherein any one of a glass substrate, a plasticsubstrate, and an SOI substrate is used as the substrate.
 5. Thesemiconductor device according to claim 1, wherein the semiconductordevice is one of an RFID tag, an ID tag, an IC tag, an IC chip, an RFtag, a wireless tag, an electronic tag, and a wireless chip.
 6. Thesemiconductor device according to claim 2, wherein the semiconductordevice is one of an RFID tag, an ID tag, an IC tag, an IC chip, an RFtag, a wireless tag, an electronic tag, and a wireless chip.